Altoona Works constructed the prototype B6 in 1902. The B6 had the Pennsylvania's trademark square-shouldered
Belpaire firebox and drivers. They were constructed as
saturated steam engines, rebuilt with
superheaters later as class
B6s, and had
Piston valves and
Stephenson valve gear. A total of 79 were built by
Baldwin and
Lima, in addition to Altoona, between 1902 and 1913. The next version built was the
B6sa, 55 of which were built at Altoona during 1913–1914. These had
radial-stay fireboxes, common elsewhere but rare on the Pennsylvania, and they replaced the Stephenson gear with the more modern
Walschaerts valve gear. Steam delivery pipes were outside, like all other PRR modern power. All were built superheated. Finally, during 1916–1920, 238 of class
B6sb were built. These were the final, definitive type, and had a Belpaire firebox, but were otherwise little changed from the B6sa. The final 97 locomotives had piston valves mounted outboard of the cylinders, instead of inbound as previously built, giving the cylinder assemblies an outward cant at the top, rather than inward. All B6sa and B6sb locomotives were retrofitted with
power reverse to make the frequent back-and-forth of switching quicker and easier. The last PRR locomotive in active service was #5244, leased to Union Transportation of
New Egypt, New Jersey until July 1959. This was considered quite an achievement considering the Pennsylvania Railroad's extensive steam program. In 1939, toy train manufacturer Lionel introduced their version of Pennsy's B6 in several variations including a scale version (scale couplers and smaller flanges to operate on special track) along with six versions of what would later become known as "semi-scale." Two B6s survive: - B6sb #1670 was saved in the PRR's historic collection at
Northumberland, Pennsylvania and was donated to the
Railroad Museum of Pennsylvania along with the majority of that collection. - B6sa #60 was on a siding in Hockessin, Delaware, along the
Wilmington and Western Railroad. It has a larger tender, from a 2-8-0 Consolidation, but it is intact, albeit in poor condition. In 2019–2020, it was donated to the Historic Red Clay Valley Inc., and the locomotive remains on a siding near Mt. Cuba. B6sa #60 then was moved to the Wilmington and Western's railroad shops in Wilmington, Delaware on May 9, 2024 where it will be cosmetically restored and then put on display as an exhibit in Lewes, Delaware. == Notes ==